The present invention relates to an apparatus for conveying presensitized lithographic printing plates.
Generally speaking, a presensitized lithographic printing plate has an aluminum support plate on which photosensitive resin layers are formed. The size of the presensitized lithographic printing plate is usually pretty large. To be more specific, the size of the plate is approximately 1 m.times.1 m. Furthermore, its weight is 500 to 1000 g per plate.
Up to the present, when presensitized lithographic printing plates are stored or conveyed, a suitable number of plates are piled up, horizontally with interleaves inserted between each plate.
However, the use of interleaves in order to prevent damage to the printing plate surface greatly reduces working efficiency, when the printing plates are piled up and taken out from the pile.
Recently, in order to improve the situation, the apparatus shown in FIG. 9 has been adopted. In FIG. 9, the presensitized lithographic printing plates 1, 1, . . . are horizontally piled without inserting interleaves and they are strongly squeezed by the rigid end plates 2, 2 which are located at both the upper side and the lower side and clamped tightly by the bolts 3, 3, . . . . In this way, the pile of plates becomes a solid pallet and scratches on the surfaces of the presensitized lithographic printing plates caused by slippage of the plates, created by vibration, can be prevented.
In this case, one of the end plates 2 functions as a pallet board, and a cardboard sheet 4 is put at least between one of the surfaces of a pile of the presensitized lithographic printing plates 1, 1 . . . and one of end plates 2, 2 in order to prevent damage of the printing plate surfaces. The number of the plates in the pile is usually 700 to 1500 When the pile is conveyed, a forklift is used as the weight of 1000 plates is 500 to 1000 kg.
However, in the case of using the above-mentioned end plates and piling the presensitized lithographic printing plates horizontally, the first problem is the area needed to store the pile, which must be more than 1 m.times.1 m. The second problem is that when 700 to 1500 printing plates are conveyed close to the plate processing machine (the developer and the printer), they are actually fed to the machine by hand. About 50 plates are put against a stand close to the plate making machine, and the photosensitive resin surfaces of the plates must be taken care of so as not to be damaged. The plates must be taken out to be used one by one from a group of plates leant against the stand. As a result, the working efficiency is low and the printing plates need to be handled carefully. Although the number of plates is about 50, their weight is pretty heavy and workers are subjected to hard work. Furthermore, in order to take out a pile of 50 plates, a cardboard sheet must be inserted beforehand to the pile every 50 printing plates when the plates are piled, which leads to an increase of production costs.
The third problem relates to the second problem. The printing plates, the number of which is 700 to 1500, are conveyed in a stack to the plate processing machine by a fork lift. But human power is needed when the printing plates are fed to the plate processing machine. For that reason, the printing plates cannot be conveyed smoothly by the above-mentioned plate handling system.
The fourth problem is that unless the end plates 2, 2 are clamped firmly, some printing plates slip during conveyance and the surfaces of the presensitized lithographic resin layer tend to be easily damaged. When the end plates are strongly clamped by the bolts, but small foreign particles are between the plates, the surfaces of the resin layers are apt to be damaged as the interlief is not used between the printing plates. Even before the end plates are clamped, the lower printing plates of the pile are easily damaged because of the weight of the upper printing plates.